1. Field of the Invention
The present invention relates to an optical pulse testing device for use in measuring various properties of an optical fiber to be measured, on the basis of a returned light of an optical pulse that is obtained from the optical fiber to be measured.
2. Description of the Related Art
As well known in the art, an optical pulse testing device is a device for detecting a back scattered light and a reflected light at each point where an optical pulse passes through in an optical fiber to be measured, to measure various properties of the optical fiber to be measured. In one of the optical pulse testing devices, it is known to detect returned lights whose wavelengths are different from one another, in order to measure a particular property. Inasmuch as propagation rate is dependent on the wavelength of each light in the optical fiber to be measured, returned lights whose wavelengths are different from one another are returned back from points (return points) which are different from one another, when the returned lights are detected at a time. As a result, it is impossible to exactly detect the properties of the optical fiber to be measured, inasmuch as error occurs in each of the return points in case of detecting the returned lights whose wavelengths are different from one another, at a same time.
Taking the above-mentioned problem into consideration, it is an object of the present invention to provide an optical pulse testing device capable of improving a measuring precision in case of measuring properties of an optical fiber to be measured, in accordance with returned lights which have wavelengths different from one another.
In order to accomplish the above-mentioned object, an optical pulse testing device is for inputting an optical pulse to an optical fiber to be measured, to detect returned lights which have wavelengths different from one another and which are returned back from passing points in the optical fiber to be measured, respectively. The optical pulse testing device measures properties of the optical fiber to be measured, in accordance with detection results of the returned lights, wherein the optical pulse testing device detects each of the returned lights at a timing based on a difference among propagation rates in the optical fiber to be measured, to compensate an error of a return point in each returned light.
The optical testing device may adjust a timing relationship among sampling pulses which are established in the returned lights, respectively, on the basis of the difference among the propagation rates of the returned lights, to compensate the error of the return point in each return light.
The optical pulse testing device may periodically carry out a phase-shift of other sampling pulses with respect to one sampling pulse to adjust the timing relationship among the sampling pulses.
The optical pulse testing device may periodically carry out a phase shift of the timing relationship among the sampling pulses on the basis of a count value of reference clock after inputting the optical pulse into the optical fiber to be measured.
The optical pulse testing device may periodically delay other sampling pulses with respect to one sampling pulse to carry out a phase shifting.
According to the present invention, an optical pulse testing device is for inputting an optical pulse which has one selected from a plurality of wavelengths to an optical fiber to be measured, to detect returned lights which are returned back from passing points in the optical fiber to be measured, respectively. The optical pulse testing device measures properties of the optical fiber to be measured, in accordance with detection results of the returned lights, wherein the optical pulse testing device adjusts a detection timing of returned lights corresponding to an optical pulse having another wavelength, with respect to a detection timing of returned lights corresponding to an optical pulse having a reference wavelength selected from the plurality of wavelengths, in accordance with a difference among the propagation rates of the wavelengths, to compensate an error of a return point in each returned light.
The optical testing device may adjust a timing relationship among sampling pulses which are established in the returned lights, respectively, on the basis of the difference among the propagation rates of the returned lights, to compensate the error of the return point in each return light.
The optical pulse testing device may periodically carry out a phase shift of other sampling pulses which are established to returned lights corresponding to optical pulses having other wavelengths, with respect to one sampling pulse which is established to the returned lights corresponding to the optical pulse having the reference wavelength, to adjust the timing relationship among the sampling pulses.
The optical pulse testing device may periodically carry out a phase shift of the timing relationship among the sampling pulses on the basis of a count value of reference clock after inputting the optical pulse into the optical fiber to be measured.
The optical pulse testing device may periodically delay other sampling pulses with respect to one sampling pulse to carry out a phase shifting.